The aforementioned '712 patent teaches the irradiation of naturally occurring or raw plant material which provides fibers characterized by the growth of layers of cellulose building up cell walls. This growth of cellulose fibers occurs in farmed crops such as cotton, jute, hemp, sisal and the like, which are commonly used to make cordage and rope in a wide range of diameters and tensile strengths. Making rope requires twisting relatively short cellulose fibers of one or more of the foregoing naturally occurring fibers into yarn, then twisting multiple yarns into rope. Having expended the energy and cost to make rope it is self-evident that one would not go to the trouble and expense of making rope if one then deliberately intended to convert the rope into fibers.
As described in the pending '452 application, chopping a mass of cotton fibers into small squares in the range from 6.35 mm (0.25″) to 12.7 mm (0.5″) in length in a HOG or Cumberland chopper, and feeding the squares to a micronizer results in micronized particles having a narrow size range in which at least 90% by weight of the micronized particles are less than 10 μm in length, and the average length of all particles is in the range from about 4-5 μm. The '452 application also teaches that rope may be micronized after being first committed with an inline cutter having a rotary blade and six knives, a bed knife, a 22 HP motor and a custom feed tube with six 6 feed tubes each having a diameter of 19.05 mm (0.75″). The cutter motor is controlled by a variable frequency drive unit, and the rotary speed of the cutter and the lineal feed rate of the pinch roll feed unit determines the cut length of the fibers which is typically 6.35 mm (0.25″). The novel rope-on-spool uncoiler and granulator system disclosed herein can, if desired, provide chopped fibers in the same size range. However, this cut length of fibers is found to be too long to be fed to the micronizer, as are fibers 3.18 mm (0.125″) or longer, if the micronizer is to produce more than 90% of the micron-sized fragments collected from its discharge in a critically small length less than 3.18 mm (0.125″) at a production rate in excess of 22.7 Kg/hr (50 lb/hr)—this production rate being found essential for a commercially economic system
It is only the foregoing discovery, namely that the cutter described in the system of the foregoing '452 application did not produce the fragments in the desired size range for most efficiently feeding the micronizer, that gave rise to the unique situation which requires committing the rope in a particular range of diameters at an economical rate using a better system.
This novel and improved rope handling system is designed and constructed because it was discovered that a rotary blade cutter of different construction could extend the limit of how small the tiny fragments could be made before they were fed to the micronizer, and that a different configuration of a train of pulleys (compared to that of the '452 system) provided a more efficient and economical system.
Moreover, as disclosed in the '452 application, it was found that when cellulose fiber rope is exposed to electron beam radiation to receive a dosage in the range from about 30 to 100 MegaRads, the rope is degraded so as to require controlling the tension under which it is uncoiled from a spool before it is chopped up. The term “chopped up” is used to refer to fragments generated by the action of a rotary blade cutter as opposed to the term “micronized” which is used herein to refer to particles or granules generated by the action of the micronizer. It is to be noted that the micronizer does not have blades but relies on the energy of high pressure air to cause fiber fragments to collide with each other at such high velocity as to break them up into even smaller fragments referred to as “granules”. When a mass of naturally occurring relatively long cellulose fibers longer than about 6.35 mm (0.25″) is fed directly to the micronizer, it typically generates fragments more than 75% of which are no shorter than 70 μm (micrometers or microns) even if the micronizer is allowed to run for an optimum period to generate these small fragments. When such long natural cellulose fibers are micronized beyond the optimum period, the fibers form a matte in the mill, and cannot be reduced to a smaller size. Such small fragments about 70 μm long, or longer, are used to enhance the function of drilling mud currently used in down hole drilling fluids in oil rigs and the like. When substrate is removed from a down hole, pumping clay into the down hole lowers the viscosity of the substrate and clay suspension as it flows through a discharge pipe. The combination of clay and cellulose fibers maintains the removed substrate as a suspension while maintaining a desirably low viscosity.
Because the rotary blade cutter used herein converts rope fed to it into granules, it is referred to as a “granulator”. However, it is to be noted that it is a commercially available machine identified as a Model 811 Series Inline Granulator (available from Precision Airconvey Corporation) driven by a direct drive 5 HP motor at 1750 RPM, which machine is conventionally used to shred scrap synthetic resinous film typically less than 50.8 μm (2 mils) thick, into small strips which can be recycled. It is used herein by adjusting the edge of a stationary bed knife to be uniformly spaced at a cutting clearance no more than 25.4 μm (0.001″), preferably 12.7 μm (0.5 mil 0.0005″) or less, from the edges of plural rotatable blades, so that the cellulose fibers are chopped into tiny fragments, the closer the cutting clearance, the smaller the length of the fibers. It is found that by equipping the machine with a screen having either a 6.35 mm (0.25″) or 3.18 mm (0.125″) mesh openings, either fragments no longer than 6.35 mm or 3.18 mm respectively, may be allowed to pass through the screens, the remaining longer fragments being chopped up into smaller ones until they pass through the screen chosen.